We use a 20-site pro license to manage email on the new server clusters via the WP Mail SMTP Pro service.
You will need to network activate the plugin and get the site license key to enable it.
Use Amazon SES service to send email. To configure you will need the Access Key and Secret Access key to set this up. These are in Lance’s password manager app — or you will need to create a new identity under the storelocatorplus.com domain in SES and create a new key pair.